1. Field of the Invention
The present invention relates to connectors and other threaded mechanisms, and more particularly, relates to threaded connectors and threaded mechanisms that incorporate mating sets of dual synchronized threads for effecting the union between the threaded connections.
2. Description of the Prior Art
It is well known in the prior art to have a tube, pipe or other cylindrical object that incorporates dual threads. That is, a portion of the external surface of the pipe includes male threads, and a portion of the internal surface of the pipe includes female threads. Such dual-threaded cylindrical devices are typically utilized wherein a cap or cover screws onto the end of the pipe or tube utilizing the external male threads, and the internal female threads are utilized for providing a screw-adjustment to an internal mechanism where the tube or pipe is connected. An example is a fluid pressure relief valve, wherein the relief pressure is adjustable by turning a threaded plug or the like within the internally threaded tube, the threaded plug engaging a spring and ball mechanism that defines the relief valving mechanism, the screw-adjustment mechanism within the tube being environmentally protected by a cap that screws over the end of the pipe or tube, utilizing the external male threads of the pipe or tube. Another example is the valve stem used on vehicle tires and wheels, wherein the internally threaded portion of the cylindrical valve stem is utilized to threadedly receive therein the valve core element which defines the closure mechanism for the valve stem, and the external male threads on the end of the cylindrical valve stem receive thereon the plastic or metal cap which is an environmental seal for the valving mechanism within the valve stem.
In these prior art dual thread applications, the internal and external threads function independently of each other, the internal threads serving a function related to the operation of the device itself, and the external threads simply serving as a means to attach a protective environmental cover over the internal mechanism.
In many prior art fluid devices (pumps, valves, motors, etc.), the device includes a cap or cover plate that must effectively seal the inner workings of the device. Such a cap or cover plate generally covers and seals a portion of the device body that needs to be accessible for purposes of manufacture, assembly, adjustment, etc. Many times these caps or plates are made of a different material from that of the device body. In such instances, differences in rates and amounts of material expansion and contraction between the cap or plate and the fluid device body occur because of applications of the fluid device in extremely high or low temperature environments, in high pressure environments, and/or due to water absorption by plastic components. In addition, conventional connector caps or nuts are generally of thinner wall construction than the bodies or mating connectors, and therefore tend to expand as the cap or nut is tightened. In such instances (threaded caps or plates expanding different amounts and at different rates), thread separation occurs, thereby jeopardizing the fluid seal between the cap and plate or fluid device body.